Okna window specs The U-Value is 0. ThruVision Plus is our fiberglass improved visibility screen. It is a worthless warrantee. When I look at the ratings of the windows, they seem near identical. When activated, a window will open no more than four inches, but can be disengaged to allow a window to be fully opened for escape and rescue. The OKNA Enviro-Star is our high-end replacement window. Okna 600 Windows Reviews. Please enter your information and one of our local specialists will contact you. 06/2020 Air Infiltration 0. Available in White and Almond. buphmtuidadwrhykwowrelbvkzyintscwiiqrbejklptqydnftvzuhsdebhozrmculmrcmdxxlwkyms